Feedback based indoor localization using digital off-air access units

ABSTRACT

A system for indoor localization using satellite navigation signals in a Distributed Antenna System includes a plurality of Off-Air Access Units (OAAUs). Each of the plurality of OAAUs is operable to receive an individual satellite navigation signal from at least one of a plurality of satellites and operable to route signals optically to one or more DAUs. The system also includes a plurality of remote DRUs located at a remote location. The plurality of remote DRUs are operable to receive signals from a plurality of local DAUs. The system further includes an algorithm to delay each individual satellite navigation signal for providing indoor localization at each of the plurality of DRUs and a GPS receiver at the remote location used in a feedback loop with the DRU to control the delays.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/171,600, filed Feb. 3, 2014; now U.S. Pat. No. 9,476,984, whichclaims priority to U.S. Provisional Patent Application No. 61/761,183,filed on Feb. 5, 2013, the disclosures of which are hereby incorporatedby reference in their entirety.

BACKGROUND OF THE INVENTION

Global Positioning System (GPS) technologies, initially utilized bymilitary organizations, including the U.S. Department of Defense, havenow achieved widespread use in civilian applications. The widespreadavailability of GPS has enabled the provision of many location-basedservices, providing location information for mobile devices.

Although GPS provides high accuracy in positioning when outdoors, theGPS signal may not be received with sufficient strength and from enoughsatellites when a user is inside a building or structure. An indoorpositioning system (IPS) is a network of devices used to locate objectsor people inside a building. Currently, no standard for an IPS has beenadopted in a widespread manner, adversely impacting deployment.

An IPS typically relies on anchors with known positions rather thanrelying on satellites, since satellite signals are not typicallyavailable at indoor positions as a result of signal attenuationresulting from roofs and other building structures. Despite the progressmade in IPS design and implementation, there is a need in the art forimproved methods and systems related to indoor localization.

SUMMARY OF THE INVENTION

The present invention generally relates to wireless communicationsystems employing Distributed Antenna Systems (DAS) as part of adistributed wireless network. More specifically, the present inventionrelates to a DAS utilizing a digital Off-Air Access Unit (OAAU). In aparticular embodiment, the present invention has been applied to receiveGPS signals at the OAAUs that can be configured in a star configurationor a daisy chained configuration. The methods and systems describedherein are applicable to a variety of communications systems includingsystems utilizing various communications standards.

Satellite navigation systems, including the Global Positioning System(GPS) have received widespread use in many applications such as trafficmanagement, navigation, medical emergency services as well as locationbased services for handsets. GPS is discussed herein as an exemplarysatellite navigation system, although other systems, including GLONASS(Russian), Galileo (Europe), QZSS (Japanese), and BeiDou (Chinese) areincluded within the scope of the present invention and should beunderstood to fall under the umbrella of systems collectively referredto as GPS herein. Although GPS positioning is prevalent in outdoorapplications, indoor localization using GPS is not common because of thelarge signal attenuation caused by the building walls. Most indoorpositioning solutions require unique infrastructure that is complicatedand expensive to deploy. The indoor positioning architecture provided byembodiments of the present invention uses the existing GPS Satelliteinfrastructure and can be used with standard handsets that contain GPSreceivers.

A distributed antenna system (DAS) provides an efficient means ofdistributing signals over a given geographic area. The DAS networkcomprises one or more digital access units (DAUs) that function as theinterface between the Off-Air Access Units (OAAU) and the digital remoteunits (DRUs). The DAUs can be collocated with the Off-Air Access Units(OAAU). Under certain embodiments, the Off-Air Access Units may not becollocated with the DAUs. Off-Air Access Units can be used to relay GPSSatellite signals to one or more DAUs. Under certain embodiments theOff-Air Access Units may relay the GPS signals directly to one or moreDigital Remote Units (DRUs). One or more Off-Air Access Units can beused to communicate with one or more Satellites. The Off-Air AccessUnits relay the RF GPS signals between the Satellite and the coveragearea.

According to an embodiment of the present invention, a system for indoorlocalization using satellite navigation signals in a Distributed AntennaSystem is provided. The system includes a plurality of Off-Air AccessUnits (OAAUs). Each of the plurality of OAAUs is operable to receive anindividual satellite navigation signal from at least one of a pluralityof satellites and operable to route signals optically to one or moreDAUs. The systems also includes a plurality of remote DRUs located at aRemote location. The plurality of remote DRUs are operable to receivesignals from a plurality of local DAUs. The system further includes analgorithm to delay each individual satellite navigation signal forproviding indoor localization at each of the plurality of DRUs.

According to an embodiment of the present invention, a system for indoorlocalization using satellite navigation signals in a Distributed AntennaSystem is provided. The system includes a plurality of Off-Air AccessUnits (OAAUs). Each of the plurality of OAAUs is operable to receive anindividual satellite navigation signal from at least one of a pluralityof satellites and operable to route signals optically to one or moreDAUs. They system also includes a plurality of remote DRUs located at aremote location. The plurality of remote DRUs are operable to receivesignals from a plurality of local DAUs. The system also includes analgorithm to delay each individual satellite navigation signal forproviding indoor localization at each of the plurality of DRUs and a GPSreceiver at the remote location used in a feedback loop with the DRU tocontrol the delays.

According to another embodiment of the present invention, a system forindoor localization using GPS signals in a Distributed Antenna System isprovided. The system includes a plurality of Off-Air Access Units(OAAUs) connected together via a daisy chain configuration and operableto receive a GPS signal from at least one of a plurality of GPSsatellites, and operable to route signals optically to one or more DAUs.The system also includes a plurality of remote DRUs located at a remotelocation. The plurality of remote DRUs are operable to receive signalsfrom at least one of the one or more DAUs. The system further includesan algorithm to delay the GPS signals received at the plurality of OAAUsfor providing indoor localization at each of the plurality of remoteDRUs and a GPS receiver at the remote location used in a feedback loopwith the plurality of remote DRUs to control the delays

According to yet another embodiment of the present invention, a systemfor indoor localization using GPS signals in a Distributed AntennaSystem is provided. The system includes a plurality of Multiple InputOff-Air Access Units (OAAUs), receiving a GPS signal from at least oneof a plurality of GPS satellites and operable to route signals opticallyto one or more DAUs, and a plurality of remote DRUs located at a remotelocation. The plurality of remote DRUs are operable to receive signalsfrom one or more of the one or more DAUs. The system also includes analgorithm to delay each individual GPS satellite signal for providingindoor localization at each of the plurality of DRUs and a GPS receiverat the remote location used in a feedback loop with the DRU to controlthe delays

According to a particular embodiment of the present invention, a systemfor indoor localization using satellite navigation signals in aDistributed Antenna System is provided. The system includes a pluralityof Off-Air Access Units (OAAUs), each of the plurality of OAAUs operableto receive an individual satellite navigation signal from at least oneof a plurality of satellites and operable to route signals optically toone or more DAUs. The satellite navigation signals may be associatedwith one of several systems, including GPS, GLONASS, Galileo, QZSS, orBeiDou. The system also includes a plurality of Off-Air Access Units(OAAUs). Each of the plurality of OAAUs is operable to receive theindividual satellite navigation signal from at least one of theplurality of satellites and operable to route signals optically to oneor more DAUs. The system further includes a plurality of remote DRUslocated at a Remote location. The plurality of remote DRUs are operableto receive signals from a plurality of local DAUs. Moreover, the systemincludes an algorithm to delay each individual satellite navigationsignal for providing indoor localization at each of the plurality ofDRUs and a GPS receiver at the remote location used in a feedback loopwith the DRU to control the delays.

According to a specific embodiment of the present invention, a systemfor indoor localization using GPS signals in a Distributed AntennaSystem is provided. The system includes a plurality of satellites, eachtransmitting a GPS signal and a plurality of Off-Air Access Units(OAAUs) operable to receive a GPS signal from at least one of theplurality of GPS satellites. The OAAUs are also operable to routesignals directly to one or more DRUs.

According to another specific embodiment of the present invention, asystem for indoor localization using GPS signals in a DistributedAntenna System is provided. The system includes a plurality ofsatellites, each transmitting a GPS signal and a plurality of Off-AirAccess Units (OAAUs), receiving at least one of the plurality of GPSsatellites, and operable to route signals optically to one or more DAUs.The system also includes a plurality of remote DRUs located at a Remotelocation. The plurality of remote DRUs are operable to receive signalsfrom a plurality of local DAUs. The system further includes ade-multiplexer to extract one of the GPS satellite signal's and timedelay it at each DRU, an algorithm for determining the delay at each ofthe plurality of DRUs to provide indoor localization, and a GPS receiverat the remote location used in a feedback loop with the DRU to controlthe delays

Numerous benefits are achieved by way of the present invention overconventional techniques. Traditionally, an Off-Air GPS Repeatercommunicates with the satellite via a wireless RF signal andcommunicates with the coverage area via a wireless RF signal. Off-AirGPS repeaters broadcast the GPS Satellite signal indoors, which providesthe GPS Handset receiver with the position of the Off-Air Repeater. Insome embodiments, no additional intelligence is used to provide anypositional information for the location of the indoor user relative tothe Off-Air Repeater. An Off-Air Access Unit (OAAU) relays the GPSsignals to a DAU via an optical cable. The GPS signals from the Off-AirAccess Unit are transported digitally over an optical cable to one ormore DAUs or directly to one or more Digital Remote Units (DRU).Transporting the Off-Air Access Unit signals optically provides anadditional benefit of enabling time multiplexing of multiple GPS signalsfrom multiple Off-Air Access Units. Additionally, embodiments enable therouting of the Off-Air Access Unit signals to one or more remotelocations. Utilizing multiple GPS signals from multiple OAAUs canprovide enhanced indoor localization accuracy.

GPS positional information has a stringent requirement for accuracy inorder to enable First Response providers (911) to quickly and accuratelylocate the position of the emergency. According to an embodiment of thepresent invention, a feedback mechanism is utilized to insure accuracyof the GPS positional information. The feedback mechanism involves theuse of a GPS receiver at the remote location in a closed loop with theDigital Remote Unit (DRU) broadcast of the Off-Air GPS signals. Anysignificant error between the DRU broadcast GPS position and the storedpredefined GPS position can be measured and utilized to produce analarm. Thereby the equipment maintenance staff can be notified ofproblems. These and other embodiments of the invention along with manyof its advantages and features are described in more detail inconjunction with the text below and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the basic structure and an example ofthe transport routing based on having a 3 GPS satellites with 3 DigitalAccess Units (DAUs) at a local location, 3 Off-Air Access Units (OAAUs)at a local location and Digital Remote Units (DRUs) at a remote locationaccording to an embodiment of the present invention. In this embodiment,3 OAAUs are connected to a DAU at the local location.

FIG. 2A is a block diagram showing the basic structure and an example ofthe transport routing based on having a 3 Satellites with 3 DAUs at alocal location, 3 OAAUs daisy chained together at a local location andoptical interfaces to DRUs at the remote locations according to anembodiment of the present invention.

FIG. 2B shows the data transport structure whereby the various SatelliteGPS signals are time-multiplexed into a frame according to an embodimentof the present invention.

FIG. 3 is a block diagram showing the basic structure and an example ofthe transport routing based on having multiple OAAUs at local locationswith multiple DAUs at a local location, and multiple Digital RemoteUnits (DRUs) at a remote location and optical interfaces to the Remotesaccording to an embodiment of the present invention.

FIG. 4 is a block diagram illustrating a DAU, which contains physicalNodes and a Local Router, according to an embodiment of the presentinvention.

FIG. 5 is a block diagram illustrating a Off-Air Access Unit (OAAU),which contains physical Nodes and a repeater router, according to anembodiment of the present invention.

FIG. 6 is a simplified flowchart illustrating the data flow structurebetween the Off-Air Access Unit (OAAU) and the DAU or another RDUaccording to an embodiment of the present invention.

FIG. 7 is a block diagram showing the basic structure and an example ofthe transport routing based on having multiple OAAUs at local locationswith multiple Digital Remote Units (DRUs) at a remote location andoptical interfaces to the Remotes according to an embodiment of thepresent invention.

FIG. 8 is a block diagram showing the basic structure and an example ofthe transport routing based on a single OAAUs with 3 receivers at thelocal location with multiple DAUs at a local location, and multipleDigital Remote Units (DRUs) at a remote location and optical interfacesto the Remotes according to an embodiment of the present invention.

FIG. 9 is a conceptual building layout showing 2 OAAUs receiving the GPSsignals from a subset of Satellites and transporting those signals tothe Digital Remote Units (DRU) via optical cables according to anembodiment of the present invention. The remote signals at the DRUs arebroadcast over the antennas and received by the users GPS receiver inthis embodiment.

FIG. 10 is a block diagram according to one embodiment of the inventionshowing the basic structure whereby the OAAU GPS signals on the Frameare time de-multiplexed, delayed relative to one another and thencombined according to an embodiment of the present invention.

FIG. 11 is a block diagram showing the basic structure whereby one ofthe OAAU GPS signals on the Frame is time de-multiplexed, delayed andthen transmitted at one of more DRUs according to an embodiment of thepresent invention. The GPS signals for the individual satellites aretransmitted on separate DRUs for the objective are replicating thesatellite configuration indoors in this embodiment.

FIG. 12 is a block diagram showing the basic structure whereby the OAAUGPS signals on the Frame are time de-multiplexed, delayed relative toone another and then combined according to an embodiment of the presentinvention. Each DRU is fed a distinct combination of Satellite GPSsignals in this embodiment.

FIG. 13 is a block diagram showing the DRU GPS transmitter in a feedbackloop that is driven by the error between the GPS Receiver position andthe predefined position that is stored on the server according to anembodiment of the present invention.

FIG. 14 is a block diagram showing an adaptive loop used to determinethe Delay values for the individual Satellite GPS signals according toan embodiment of the present invention. The position error resultingfrom the difference between the Measured GPS position and the predefinedGPS position is used to optimize the Delays for the various SatelliteGPS signals.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

A distributed antenna system (DAS) provides an efficient means oftransporting signals between local units and remote units. The DASnetwork comprises one or more digital access units (DAUs) that functionas the interface between the Off-Air Access Units (OAAU) and the digitalremote units (DRUs). The DAUs can be collocated with the Off-Air AccessUnits (OAAU). The DRUs can be daisy chained together and/or placed in astar configuration and provide coverage for a given geographical area.The DRUs are typically connected with the DAUs by employing a high-speedoptical fiber link. This approach facilitates transport of the RFsignals from the Off-Air Access Units (OAAU) to a remote location orarea served by the DRUs.

Off-Air Access Units communicate with one of more GPS Satellites overthe air. Off-Air Access Units are convenient for relaying GPS signalsbetween locations that are not well covered by the GPS Satellite itself.A typical Off-Air Access Unit receives the Downlink RF GPS signal from aSatellite, amplifies and filters the RF signal and transports it to aDRU for a given coverage area. Each Off-Air Access Unit utilizes adirectional antenna to communicate with a distinct subset of GPSSatellites. Typically, a minimum of 3 GPS Satellites are used totriangulate and determine the receiver's position. The relativetime-delays between the 3 GPS Satellites provide a means of identifyingthe 2D position of the receiver. 4 GPS Satellite signals will provide 3Dlocalization of the receiver. Directional antennas are used at theOff-Air Access Units in order to separate the 3 or more Satellitesignals. Each GPS Satellite signal will be time multiplexed in a datatransport frame structure and sent to the remote DRUs. It is assumedthat the DRUs position is known a-priori. The DRU's will receive theindependent GPS satellite signals, which are independently time-delayed,for example, by a user, in order to replicate the GPS position of theDRUs. The GPS positional information of each DRU can be determined froma 3D map of the given indoor venue. One embodiment of the presentinvention enables a GPS receiver to be incorporated in both the DRU aswell as the Off-Air Access Units. The absolute GPS position of the DRUscan be obtained be using the Off-Air Access unit GPS positioninformation and then adjusting it to the 3D position offset inside thevenue (e.g., 4^(th) floor, 30 m North, 10 m West). Locating a GPSreceiver at the DRU will provide a feedback mechanism of insuring theaccuracy of the user-established time-delays in some embodiments.

FIG. 1 illustrates a DAS network architecture according to an embodimentof the present invention and provides an example of a data transportscenario between 3 GPS Satellites, multiple Off-Air Access Units(OAAUs), multiple local DAUs, and multiple DRUs. GPS Satellites 1,2 and3 are connected to OAAU 1 (120), OAAU 2 (121), and OAAU 3 (131),respectively, by wireless links in the illustrated embodiment. DAUs 1(102), (108) and DAU 3 route the Off-Air Access Unit signals to thevarious DRUs. Each of the local DAUs is connected to server (150). Inthis embodiment, the OAAUs are connected in a star configuration withDAU (102) using optical cables (i.e., optical fibers). Although threesatellites are illustrated in FIG. 1, the illustrated three satellitesare shown merely as an example and it will be appreciated thatadditional satellites (e.g., 4, 5, or more satellites) in theconstellation can be utilized by embodiments of the present invention.In the following figures, three exemplary satellites are illustrated,but the embodiments illustrated in the following figures are not limitedto the use of only three satellites. One of ordinary skill in the artwould recognize many variations, modifications, and alternatives.

One feature of embodiments of the present invention is the ability toroute the GPS Satellite signals among the DAUs and DRUs. In order toroute GPS signals available from one or more Satellites, it is desirableto configure the individual router tables of the DAUs and DRUs in theDAS network. This functionality is provided by embodiments of thepresent invention.

The DAUs are networked together to facilitate the routing of signalsamong multiple DAUs. This architecture enables the various GPS Satellitesignals to be transported simultaneously to and from multiple DAUs. PEERports are used for interconnecting DAUs in some implementations.

The DAS network can include a plurality of OAAUs, DAUs and DRUs. The DAUcommunicates with the network of DRUs and the DAU sends commands andreceives information from the DRUs. The DAUs include physical nodes thataccept and deliver RF signals and optical nodes that transport data. ADAU can include an internal server or an external server. The server isused to archive information in a database, store the DAS networkconfiguration information, and perform various data related processingamong other functions.

Additionally, the OAAU communicates with the DAU. The OAAU receivescommands from the DAU and delivers information to the DAU. The OAAUsinclude physical nodes that accept GPS RF signals and optical nodes thattransport data.

In some embodiments, it is possible to store the GPS signals in memory(e.g., in the DRUs) and then disconnect the Off-Air Access units. Inthese embodiments, once the GPS signals are stored in memory at theDRUs, it is not necessary to continuously operate the repeaterfunctionality. Rather, the DRUs can broadcast the GPS signals that arestored in the DRU's memory. Moreover, in some particular embodiments, itis possible to create data files of the GPS signal for each DRU andupload the signal via a server to each DRU. In these particularembodiments, the use of the OAAUs can be reduced or eliminated dependingon the particular implementation.

As shown in FIG. 2A, the individual GPS signals from Satellites SAT 1,SAT 2 and SAT 3 are transported to a daisy-chained network of OAAUs.FIG. 2 demonstrates how three independent Satellites, each Satellitecommunicating with an independent OAAU, provide input into a single DAU(202). A server (240) is utilized to control the routing functionprovided in the DAS network. Referring to FIG. 2A and merely by way ofexample, DAU 1 (202) receives downlink GPS signals from thedaisy-chained network of OAAUs (220, 221, 222). OAAU 1 (220) translatesthe RF signals to optical signals for the downlink. The optical fibercable (224) transports the SAT 1 signals between OAAU 1 (220) and OAAU 2(221). The optical signals from OAAU 1 (220) and OAAU 2 (221) aremultiplexed on optical fiber (225). The other OAAUs in the daisy chainare involved in passing the optical signals onward to DAU 1 (202). DAU 1(202) DAU 2 and DAU 3 transport the optical signals to and from thenetwork of DRUs. As shown in FIG. 2B, the various GPS signals from theSatellites are time multiplexed into a data stream for transportingthroughout the DAS network. Another embodiment of the present inventionincludes the use of RF connections between the OAAUs and the DAUs. Inthis embodiment the OAAU will receive the RF signals from the GPSSatellite and transport the RF signal to a DAU using an RF cable.

FIG. 3 depicts a DAS system employing multiple Off-Air Access Units(OAAUs) at the local location and multiple Digital Remote Units (DRUs)at the remote location. In accordance with the illustrated embodiment,each DRU provides unique information associated with each DRU, whichuniquely identifies data received by a particular Digital Remote Unit.In this embodiment, the individual OAAUs are independently connected toDAUs. Another embodiment of the present invention includes the use of RFconnections between the OAAUs and the DAUs. In this alternativeembodiment the OAAU will receive the RF signals from the GPS Satelliteand transport the RF signal to a DAU using an RF cable.

The servers illustrated herein, for example, server (350) provide uniquefunctionality in the systems described herein. The following discussionrelated to server (350) may also be applicable to other serversdiscussed herein and illustrated in the figures. Server (350) can beused to set up the switching matrices to allow the routing of signalsbetween the remote DRUs. The server (350) can also store configurationinformation, for example, if the system gets powered down or one DRU orOAAU goes off-line and then you power up the system, it will typicallyneed to be reconfigured. The server (350) can store the information usedin reconfiguring the system and/or the DRUs, OAAUs or DAUs.

FIG. 4 shows two of the elements in a DAU, the Physical Nodes (400) andthe Local Router (401). The Physical Nodes translate the RF signals tobaseband for the Downlink. The local Router directs the traffic betweenthe various LAN Ports, PEER Ports and the External Ports. The physicalnodes can connect to the OAAUs at radio frequencies (RF). The physicalnodes can be used for different Satellite connections.

FIG. 4 shows an embodiment whereby the physical nodes have separateinputs for the downlink paths (404). The physical node translates thesignals from RF to baseband for the downlink path. The physical nodesare connected to a local Router via external ports (409,410)). Therouter directs the uplink data stream from the LAN and PEER ports to theselected External U ports. Similarly, the router directs the downlinkdata stream from the External D ports to the selected LAN and PEERports.

In one embodiment, the LAN and PEER ports are connected via an opticalfiber to a network of DAUs and OAAUs. The network connection can alsouse copper interconnections such as CAT 5 or 6 cabling, or othersuitable interconnection equipment. The DAU is also connected to theinternet network using IP (406). An Ethernet connection (408) is alsoused to communicate between the Host Unit and the DAU. The DRU and OAAUcan also connect directly to the Remote Operational Control center (407)via the Ethernet port.

FIG. 5 shows two of the elements in a OAAU, the Physical Nodes (501) andthe Repeater Router (500). The OAAU includes both a Repeater Router andPhysical Nodes. The Repeater Router directs the traffic between the LANports, External Ports and PEER Ports. The physical nodes connectwirelessly to the GPS Satellite at radio frequencies (RF). The physicalnodes can be used for different Satellites, different antennas, etc.FIG. 5 shows an embodiment whereby the physical nodes have separateoutputs for the downlink paths (503). The physical node translates thesignals from RF to baseband for the downlink path. The physical nodesare connected to a Repeater Router via external ports (506,507). Therouter directs the downlink data stream from the LAN and PEER ports tothe selected External D ports. The OAAU also contains an Ethernet Switch(505) so that a remote computer or wireless access points can connect tothe internet.

FIG. 6 is a simplified flowchart illustrating a method of routing GPSsignals from the various Satellites to each DRU according to anembodiment of the present invention. As shown in block (619), the timemultiplexed GPS signals from the respective Satellites are time delayoffset to replicate the GPS position of the respective DRU. The DRU thenbroadcasts the GPS signal for detection by the users equipment.

FIG. 7 is a block diagram showing the basic structure and an example ofthe transport routing based on having multiple OAAUs at local locationswith multiple Digital Remote Units (DRUs) at a remote location andoptical interfaces to the Remotes according to an embodiment of thepresent invention. As shown in FIG. 7, the individual GPS signals fromSatellites SAT 1, SAT 2 and SAT 3 are transported to a daisy-chainednetwork of OAAUs. FIG. 7 demonstrates how three independent Satellites,each Satellite communicating with an independent OAAU, provide inputinto a single DRU (702). A server (740) is utilized to control therouting function provided in the DAS network. Referring to FIG. 7 andmerely by way of example, DRU 1 (702) receives downlink GPS signals fromthe daisy-chained network of OAAUs (720, 721, 722). OAAU 1 (720)translates the RF signals to optical signals for the downlink. Theoptical fiber cable (724) transports the SAT 1 signals between OAAU 1(720) and OAAU 2 (721). The optical signals from OAAU 1 (720) and OAAU 2(721) are multiplexed on optical fiber (725). The other OAAUs in thedaisy chain are involved in passing the optical signals onward to DRU 1(702). DRU 1 (702) DRU 2 and DRU 3 transport the optical signals to andfrom the network of DRUs in a daisy chain configuration.

Although three satellites are illustrated in FIG. 7 and other figuresherein, the present invention is not limited to this particular numberand additional satellites can be utilized as appropriate to theparticular application. One of ordinary skill in the art would recognizemany variations, modifications, and alternatives.

FIG. 8 is a block diagram showing the basic structure and an example ofthe transport routing based on a single OAAUs with 3 receivers at thelocal location with multiple DAUs at a local location, and multipleDigital Remote Units (DRUs) at a remote location and optical interfacesto the Remotes according to an embodiment of the present invention. Asshown in FIG. 8, the individual GPS signals from Satellites SAT 1, SAT 2and SAT 3 are transported to a single OAAU with multiple directionalantennas. FIG. 8 demonstrates an architecture in which three independentSatellites are utilized, each Satellite communicating with anindependent RF receiver in the OAAU (820). The OAAU (820)time-multiplexes the independent GPS signals to the DAS network as shownin FIG. 8.

FIG. 9 is a conceptual building layout showing 2 OAAUs receiving the GPSsignals from a subset of Satellites and transporting those signals tothe Digital Remote Units (DRU) via optical cables according to anembodiment of the present invention. The remote signals at the DRUs arebroadcast over the antennas and received by the users GPS receiver inthis embodiment. FIG. 9 shows an embodiment of the system used in athree level building. The present invention is not limited to threelevels and can be applied to buildings with additional or fewer levels.The Off-Air Access Units are located on the roof of the building and inline of sight of the Satellites. Directional antennas are used at theOAAUs in order to limit the number of Satellite GPS signals captured byeach OAAU. The objective is to separate the Satellite GPS signals ateach OAAU. The GPS signals are multiplexed on the optical fiber (941),(942) and transported to DRU 1 (931) and DRU 2 (932). The GPS signalsare de-multiplexed at each DRU and combined to create the position atthe respective DRU. The signals are broadcast through the RF antennasconnected via RF cables to the DRU. GPS Device (962) receives the signalbroadcast from DRU 2 (932) that identifies its position.

FIG. 10 is a block diagram according to one embodiment of the inventionshowing the basic structure whereby the OAAU GPS signals on the Frameare time de-multiplexed, delayed relative to one another and thencombined according to an embodiment of the present invention. As shownin FIG. 10, the GPS Satellite down stream data is de-multiplexed andeach respective GPS signal is time delayed and summed in order tosimulate the position of the DRU. Each DRU transmits the GPS position atthe respective DRU. The accuracy of the positional information at theusers GPS device is a function of the proximity to the DRU.

FIG. 11 is a block diagram showing the basic structure whereby one ofthe OAAU GPS signals on the Frame is time de-multiplexed, delayed andthen transmitted at one of more DRUs according to an embodiment of thepresent invention. The GPS signals for the individual satellites aretransmitted on separate DRUs for the objective are replicating thesatellite configuration indoors in this embodiment. As shown in FIG. 11,the GPS Satellite down stream data is de-multiplexed and each DRU timedelays and transmits one or more of the respective GPS signals. Thisembodiment enables triangulation at the users GPS device by replicatingthe Satellite signals indoors.

FIG. 12 is a block diagram showing the basic structure whereby the OAAUGPS signals on the Frame are time de-multiplexed, delayed relative toone another and then combined according to an embodiment of the presentinvention. Each DRU is fed a distinct combination of Satellite GPSsignals in this embodiment. As shown in FIG. 12, the GPS Satellite downstream data is de-multiplexed and each DRU time delays and transmits oneor more of the respective GPS signals. Each OAAU focuses on a distinctset of satellites. In this embodiment, three distinct satellite GPSsignals are received at each of the OAAU and there are three OAAUs. EachDRU transmits a unique set of Satellite GPS signals. This embodimentenables triangulation at the users GPS device by providing three uniqueGPS locations at the three DRUs. The users GPS device will average thethree GPS positions to obtain a more accurate position of the userslocation.

The position of a GPS receiver is determined by knowing its latitude,longitude and height. Four measurements are typically used to determinethe latitude, longitude, height and eliminate the receiver clock error.The GPS receiver has embedded software that has an algebraic model thatdescribes the geometrical position. For each measurement an equation ofthe distance to the satellite, p, can be written that is a function ofthe satellite position (x,y,z), the GPS receiver position (X,Y,Z) andthe clock error. For simplicity, the clock error has been removed fromeach equation below, since it is common to all equations.

$p_{1k} = \sqrt{\left( {X - x_{1} + \Delta_{1k}} \right)^{2} + \left( {Y - y_{1} + \Delta_{2k}} \right)^{2} + \left( {Z - z_{1} + \Delta_{3k}} \right)^{2}}$$p_{2k} = \sqrt{\left( {X - x_{2} + \Delta_{1k}} \right)^{2} + \left( {Y - y_{2} + \Delta_{2k}} \right)^{2} + \left( {Z - z_{2} + \Delta_{3k}} \right)^{2}}$$p_{3k} = \sqrt{\left( {X - x_{3} + \Delta_{1k}} \right)^{2} + \left( {Y - y_{3} + \Delta_{2k}} \right)^{2} + \left( {Z - z_{3} + \Delta_{3k}} \right)^{2}}$⋮$p_{Nk} = \sqrt{\left( {X - x_{N} + \Delta_{1k}} \right)^{2} + \left( {Y - y_{N} + \Delta_{2k}} \right)^{2} + \left( {Z - z_{N} + \Delta_{3k}} \right)^{2}}$where (X,Y,Z) is the position of the OAAU and (x_(N),y_(N),z_(N)) is theposition of Satellite N. and (Δ_(1k),Δ_(2k),Δ_(3k)) are the calculatedpositional offsets for DRU k. The position of DRU k is at(X+Δ_(1k),Y+Δ_(2k),Z+Δ_(3k)).

The set of four or more equations is solved simultaneously to obtain thevalues for the OAAU position (X,Y,Z). The Cartesian coordinates can beconverted to latitude, longitude, and height in any geodetic datum. Ingeneral, a procedure known as the Newton-Raphson iteration is used. Inthis procedure, each of the equations is expanded into a polynomialbased on a initial guesses of the OAAU position. Iteratively the fourequations are solved simultaneously. If either one of the height,latitude or longitude is known then only three equations are typicallyused to resolve for the OAAU position.

The calculated positional offsets, Δ's, for each DRU can be obtain fromthe blueprints of the venue and the location of the DRU in the venue.The positional offsets are converted into time delays by dividing by thespeed of light. The time delays are applied to signals (x₁, y₁, z₁) asshown in FIG. 10. The resultant signal is transmitted at the DRU andsubsequently received by the GPS device.

In some embodiments, the DAU is connected to a host unit/server, whereasthe OAAU does not connect to a host unit/server. In these embodiments,parameter changes for the OAAU are received from a DAU, with the centralunit that updates and reconfigures the OAAU being part of the DAU, whichcan be connected to the host unit/server. Embodiments of the presentinvention are not limited to these embodiments, which are described onlyfor explanatory purposes.

FIG. 13 shows an adaptive GPS repeater system that includes a GPSreceiver (1350) at the remote location along with the Digital RemoteUnit (DRU) (1300). The DRU contains an Up-Converter (UPC) (1340), whichfrequency translates the baseband signals (1330) to RF signals. Thefunction of the GPS receiver (1350) is to insure that the informationbeing transmitted by the DRU (1300) meets a predetermined level ofaccuracy. This provides a safety mechanism, whereby, if there is asignificant error between the transmitted GPS positional information andthe predefined GPS an alarm can be sent. The predefined GPS positionwill be established in the provisioning of the system and stored on theserver (1380) as well as in the DRU in some implementations. An adaptivealgorithm (1360) is used to adjust the Delay values (1320,1321,1322) ofthe GPS Satellite signals (1310,1311,1312). The Microprocessor (1370) inthe DRU controls the adaptive algorithm in some embodiments.

FIG. 14 shows a block diagram of the Feedback system used to control theSatellite GPS signal Delays (1420,1421,1422) according to an embodimentof the present invention. The GPS receiver measures the transmitted GPSsignal from the DRU and determines the position (Latitude, Longitude,Height) in block (1430). This position is compared to the known GPSposition (1450) that was established during provisioning. The resultantposition error (1440) is used to drive an adaptive algorithm such as theLeast Mean Squared (LMS) algorithm. The Delays (1420,1421,1422) areadjusted to minimize the resultant position error (1440). In the eventthat the position error is above a predefined threshold, then an alarmcan be activated. This mechanism also serves as a means of calibratingthe delays at the time of provisioning. In one embodiment of theinvention, once the delays have been determined then they can be storedin the DRU and the server and no further adaptation is required.

It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this applicationand scope of the appended claims.

What is claimed is:
 1. A method for providing feedback in a distributedantenna system, the method comprising: transmitting, by a remote unit,one or more delayed satellite navigation radio frequency (RF) signals;receiving, by a remote satellite navigation system receiver, the one ormore delayed satellite navigation RF signals; calculating, by the remotesatellite navigation system receiver, a measured geographic positioncorresponding to the one or more delayed satellite navigation RFsignals; transmitting, by the remote satellite navigation systemreceiver, the measured geographic position; receiving, by a feedbacksystem, the measured geographic position; and updating, by the feedbacksystem, a calculated delay based on the measured geographic position. 2.The method of claim 1 wherein updating the calculated delay based on themeasured geographic position further comprises: receiving apredetermined geographic position; calculating a position error valuecorresponding to the predetermined geographic position and the measuredgeographic position; and processing, by an adaptive algorithm, theposition error value, wherein the adaptive algorithm outputs a newcalculated delay.
 3. The method of claim 1 further comprising:receiving, by the feedback system, a threshold value; receiving, by thefeedback system, a predetermined geographic position; calculating, bythe feedback system, a position error value, wherein the position errorvalue is based on the measured position and the predetermined geographicposition; and transmitting a position alarm when the position errorvalue exceeds the threshold value.
 4. A method for performing indoorlocalization using satellite navigation signals in a Distributed AntennaSystem, the method comprising: receiving at each of a plurality ofOff-Air Access Units (OAAUs) an individual satellite navigation signalfrom at least one of a plurality of satellites; routing signals from theplurality of OAAUs to a plurality of Digital Remote Units (DRUs) locatedat a remote location; delaying each individual satellite navigationsignal, wherein each of the plurality of DRUs transmits one or moredelayed satellite navigation signals; receiving at a satellitenavigation system receiver at the remote location the one or moredelayed satellite navigation signals; and transmitting a measuredposition from the satellite navigation system receiver to a feedbacksystem.
 5. The method of claim 4 wherein the feedback system iscommunicatively coupled to at least one of the plurality of DRUs.
 6. Themethod of claim 4 wherein routing signals from the plurality of OAAUs tothe plurality of DRUs located at the remote location further comprises:routing signals from the plurality of OAAUs to one or more DigitalAccess Units (DAUs), wherein the DAUs are configured to route signalsbetween each of the one or more DAUs; and routing signals from the oneor more DAUs to the plurality of DRUs.
 7. The method of claim 4 furthercomprising converting the individual satellite navigation signalreceived at each of the plurality of OAAUs into a digital satellitenavigation signal.
 8. The method of claim 7 wherein the digitalsatellite navigation signal is in compliance with the Common PublicRadio Interface (CPRI) standard.
 9. The method of claim 7 whereinrouting signals from the plurality of OAAUs further comprises routingthe digital satellite navigation signal to one or more of the pluralityof OAAUs.
 10. The method of claim 7 wherein routing signals from theplurality OAAUs to the plurality of DRUs at a remote location furthercomprises: multiplexing, by at least one of the plurality of OAAUs, thedigital satellite navigation signal from each of the plurality of OAAUsto provide a multiplexed signal; and routing, by the at least one of theplurality of OAAUs, the multiplexed signal to at least one of theplurality of DRUs located at the remote location.
 11. The method ofclaim 4 further comprising: receiving, by the feedback system, athreshold value; receiving, by the feedback system, a predeterminedgeographic position; calculating, by the feedback system, a positionerror value, wherein the position error value is based on the measuredposition and the predetermined geographic position; determining that theposition error value exceeds the threshold value; and transmitting aposition alarm.
 12. A method for indoor localization using globalpositioning system (GPS) signals in a Distributed Antenna System, themethod comprising: receiving at each of a plurality of Multiple InputOff-Air Access Units (MIOAAUs) a GPS signal from at least one of aplurality of GPS satellites; routing signals from the plurality ofMIOAAUs to one or more of the plurality of MIOAAUs; routing signals fromat least one of the plurality MIOAAUs to a plurality of digital remoteunits (DRUs) located at a remote location; delaying, by at least one ofthe plurality of DRUs, each GPS signal; transmitting, by the at leastone of the plurality of DRUs, the delayed GPS signals; receiving, by aGPS receiver at the remote location, the delayed GPS signals; andtransmitting a measured position from the GPS receiver to a feedbacksystem.
 13. The method of claim 12 wherein the feedback system iscommunicatively coupled to at least one of the plurality of DRUs. 14.The method of claim 12 further comprising converting, by each of theplurality of MIOAAUs, the GPS signal into a digital satellite navigationsignal.
 15. The method of claim 14 wherein the digital satellitenavigation signal is in compliance with the Common Public RadioInterface (CPRI) standard.
 16. The method of claim 14 wherein routingsignals from the plurality of MIOAAUs further comprises routing thedigital satellite navigation signal to one or more of the plurality ofMIOAAUs.
 17. The method of claim 14 further comprising: multiplexing, byat least one of the plurality of MIOAAUs, the digital satellitenavigation signal from each of the plurality of MIOAAUs to provide amultiplexed signal; and routing, by at least one of the plurality ofMIOAAUs, the multiplexed signal to at least one of the plurality of DRUslocated at the remote location.
 18. The method of claim 12 furthercomprising: receiving, by the feedback system, a threshold value;receiving, by the feedback system, a predetermined geographic position;calculating, by the feedback system, a position error value, wherein theposition error value is based on the measured position and thepredetermined geographic position; determining that the position errorvalue exceeds the threshold value; and transmitting a position alarm.19. The method of claim 12 wherein routing signals from the at least oneof the plurality of MIOAAUs to the plurality of DRUs located at theremote location further comprises: routing signals from the plurality ofMIOAAUs to one or more Digital Access Units (DAUs), wherein the DAUs areconfigured to route signals between each of the one or more DAUs; androuting signals from the one or more DAUs to the plurality of DRUs.